issue/2135-reader-writing-blogging

Fix #2135 - problem was caused by incorrect sanitization of tag names when used in endpoints. The fix required [rewriting the sanitization routine](https://github.com/wordpress-mobile/WordPress-Android/blob/issue/2135-reader-writing-blogging/WordPress/src/main/java/org/wordpress/android/ui/reader/utils/ReaderUtils.java#L150).